Medical treatment of various illnesses and medical conditions can include continuous drug infusion into various body compartments, such as subcutaneous and intra-venous injections. Diabetes mellitus patients, for example, are generally treated by administration of varying amounts of insulin throughout the day to control their blood glucose levels. In recent years, ambulatory portable insulin infusion pumps have emerged as a superior alternative to multiple daily syringe injections of insulin. These pumps, which deliver insulin at a continuous basal rate as well as in bolus volumes, were developed to liberate patients from repeated self-administered injections and to allow them to maintain a near-normal daily routine. Both basal and bolus dose volumes are generally controlled precisely, according to individual prescription, since an overdose or under-dose of insulin or other medicinal fluids can be fatal.
Several ambulatory insulin infusion devices are currently available. These devices generally have two portions: a reusable portion that contains, a dispenser, a controller and electronics, and a disposable portion that contains a syringe-type reservoir, a needle assembly with a cannula and a penetrating member, and a fluid delivery tube. In use, a patient typically fills the reservoir with insulin, attaches the needle and the delivery tube to the exit port of the reservoir, and then inserts the reservoir into the pump housing. After purging air out of the reservoir, tube and needle, the patient inserts the needle assembly, that includes the penetrating member and cannula, at a selected location on the body and withdraws the penetrating member. To avoid irritation and infection, the subcutaneous cannula is usually replaced and discarded after a relatively short period of time, such as two to three days, together with the empty reservoir. Examples of first generation disposable syringe-type reservoir and tubes were disclosed in U.S. Pat. No. 3,631,847 to Hobbs, U.S. Pat. No. 3,771,694 to Kaminski, U.S. Pat. No. 4,657,486 to Stempfle, and U.S. Pat. No. 4,544,369 to Skakoon. The driving mechanism of these devices can be a screw thread driven plunger controlling the programmed movement of a syringe piston. Other dispensing mechanisms have been also discussed, including peristaltic positive displacement pumps, in U.S. Pat. No. 4,498,843 to Schneider and U.S. Pat. No. 4,715,786 to Wolff. These devices are generally fairly large and heavy due to the configuration and the relatively large size of the driving mechanism of the syringe and the piston. This relatively bulky device is generally carried in a patient's pocket or attached to the belt. Consequently, the fluid delivery tube is typically quite long, usually longer than 60 cm, in order to permit needle insertion at remote sites of the body. Such uncomfortable, bulky devices with a long tube are rejected by many diabetic insulin users, since they disturb regular activities, such as sleeping and swimming. Furthermore, the effect of the image projected on the teenagers'body is unacceptable. In addition, the delivery tube excludes some optional remote insertion sites, like buttocks, arms and legs.
Recently, remote controlled, skin adherable delivery devices have been introduced. Such a device generally includes a housing with a bottom surface adapted to contact a patient's skin, a reservoir disposed within the housing, and an injection needle adapted to communicate with the reservoir. These skin adherable devices also should be discarded on a relatively short duty cycle such as every two to three days for similar reasons to those discussed above for pump infusion sets. Such adherable devices have been disclosed in U.S. Pat. No. 5,957,895 to Sage, U.S. Pat. No. 6,589,229 to Connelly, and U.S. Pat. No. 6,740,059 to Flaherty. Additional configurations of skin adherable pumps have been disclosed in U.S. Pat. No. 6,723,072 to Flaherty and U.S. Pat. No. 6,485,461 to Mason. In general, these devices can be relatively bulky and expensive. Their high selling price is due to high production and accessory costs as well as the typical requirement that a user must discard the entire device, which typically includes relatively expensive components such as a driving mechanism and other electronics, every two to three days, including.